Surface plasmon resonance, fluorescence, and molecular docking studies of bovine serum albumin interactions with natural coumarin diversin

Investigation of the molecular interaction between apraclonidine, an α2-adrenergic receptor agonist, and bovine serum albumin using fluorescence and molecular docking techniques

Apraclonidine (APR) is a potent and selective α2-adrenergic receptor agonist used in the diagnosis of Horner's Syndrome, and the residuals of APR that accumulate in tissues of animals can cause central nervous and cardiovascular systems influences in humans. Therefore, to understand the influence of APR on human health, we examined the interaction of APR with the carrier protein in plasma, bovine serum albumin (BSA). The BSA fluorescence signal was quenched due to the APU-BSA complex formation and a weak binding affinity was estimated between APR and BSA. The inclusion of fluorescence, UV-vis absorption, molecular docking, and dynamics simulation techniques employed to broadly investigate the combination of APR with BSA at typical physiological conditions. The thermodynamic results revealed that enthalpy (ΔH0) and entropy (ΔS0) changes were computed as +11.14 kJ mol-1 and +97.56 J mol-1 K-1, respectively, which represented the binding is principally entropy-driven and the hydrophobic forces acting a significant role in the reaction. Analysis of synchronous and 3-D fluorescence signals revealed microenvironmental variations close to BSA's Trp and Tyr residues upon APR addition. Both the competitive site marker as well as molecular docking results detected that APR exhibited a stronger binding affinity towards Drug Site 2 (DS2) compared to Drug Site 1 (DS1).

Revealing the interaction mechanism between bovine serum albumin (BSA) and a fluorescent coumarin derivative: A multispectroscopic and in silico approach

The interaction of biomacromolecules with each other or with the ligands is essential for biological activity. In this context, the molecular recognition of bovine serum albumin (BSA) with 4-(Benzo[1,3]dioxol-5-yloxymethyl)-7-hydroxy-chromen-2-one (4BHC) is explored using multispectroscopic and computational techniques. UV-Vis spectroscopy helped in predicting the conformational variations in BSA. Using fluorescence spectroscopy, the quenching behaviour of the fluorophore upon interaction with the ligand is examined, which is found to be a static type of quenching; fluorescence lifetime studies further verify this. The binding constant is discovered to be in the range of 104 M-1, which indicates the moderate type of association that results in reversible binding, where the transport and release of ligands in the target tissue takes place. Fourier-transform infrared spectroscopy (FT-IR) measurements validate the secondary structure conformational changes of BSA after complexing with 4BHC. The thermodynamic factors obtained through temperature-dependent fluorescence studies suggest that the dominant kind of interaction force is hydrophobic in nature, and the interaction process is spontaneous. The alterations in the surrounding microenvironment of the binding site and conformational shifts in the structure of the protein are studied through 3D fluorescence and synchronous fluorescence studies. Molecular docking and molecular dynamics (MD) simulations agree with experimental results and explain the structural stability throughout the discussion. The outcomes might have possible applications in the field of pharmacodynamics and pharmacokinetics.

Turmeric: from spice to cure. A review of the anti-cancer, radioprotective and anti-inflammatory effects of turmeric sourced compounds

Turmeric (Curcuma longa) has been extensively studied for its diverse pharmacological properties, including its potential role as an anticancer agent, antioxidant, and radioprotector. This review provides an overview of the chemical composition of turmeric, focusing on its main bioactive compounds, such as curcuminoids and volatile oils. Curcumin, the most abundant curcuminoid in turmeric, has been widely investigated for its various biological activities, including anti-inflammatory, antioxidant, and anticancer effects. Numerous in vitro and in vivo studies have demonstrated the ability of curcumin to modulate multiple signaling pathways involved in carcinogenesis, leading to inhibition of cancer cell proliferation, induction of apoptosis, and suppression of metastasis. Furthermore, curcumin has shown promising potential as a radioprotective agent by mitigating radiation-induced oxidative stress and DNA damage. Additionally, turmeric extracts containing curcuminoids have been reported to exhibit potent antioxidant activity, scavenging free radicals and protecting cells from oxidative damage. The multifaceted pharmacological properties of turmeric make it a promising candidate for the development of novel therapeutic strategies for cancer prevention and treatment, as well as for the management of oxidative stress-related disorders. However, further research is warranted to elucidate the underlying mechanisms of action and to evaluate the clinical efficacy and safety of turmeric and its bioactive constituents in cancer therapy and radioprotection. This review consolidates the most recent relevant data on turmeric's chemical composition and its therapeutic applications, providing a comprehensive overview of its potential in cancer prevention and treatment, as well as in radioprotection.

Unraveling the underlying mechanism of interactions between astaxanthin geometrical isomers and bovine serum albumin

The health benefits of astaxanthin (AST) are related to its geometric isomers. Generally, functional activity is realized by the interactions between active substances and transporters. Hereto, bovine serum albumin (BSA), as a model-binding protein and transporter, is able to recognize and transport isomers of active substances through binding with them. However, differences in the binding mechanism of isomers to BSA may affect the functional activities of isomers through the "binding-transport-activity" chain reaction. Thus, this study sought to elucidate the interactions between AST geometrical isomers and BSA using multi-spectroscopy, surface plasmon resonance and molecular docking. The results showed that Z-AST displayed more interacting amino acid residues and lower thermodynamic parameters than all-E-AST. Meanwhile, the order of binding affinity to BSA was 13Z-AST (1.56 × 10-7 M) > 9Z-AST (2.70 × 10-7 M) > all-E-AST (4.01 × 10-7 M), indicating that Z-AST possessed stronger binding ability to BSA. Moreover, AST isomers were located at the junction between subdomains ⅡA and ⅢA of BSA, and showed the same interaction forces (hydrogen bond and van der Waals force) as well as kinetic processes (slow combination, slow dissociation). These interaction parameters provide valuable insights into their pharmacokinetics in vivo, and it was of great significance to explain the potential differences among AST isomers in functional activities.

Biosensing Platforms for Cardiac Biomarker Detection

Myocardial infarction (MI) is a cardiovascular disease that occurs when there is an elevated demand for myocardial oxygen as a result of the rupture or erosion of atherosclerotic plaques. Globally, the mortality rates associated with MI are steadily on the rise. Traditional diagnostic biomarkers employed in clinical settings for MI diagnosis have various drawbacks, prompting researchers to investigate fast, precise, and highly sensitive biosensor platforms and technologies. Biosensors are analytical devices that combine biological elements with physicochemical transducers to detect and quantify specific compounds or analytes. These devices play a crucial role in various fields including healthcare, environmental monitoring, food safety, and biotechnology. Biosensors developed for the detection of cardiac biomarkers are typically electrochemical, mass, and optical biosensors. Nanomaterials have emerged as revolutionary components in the field of biosensing, offering unique properties that significantly enhance the sensitivity and specificity of the detection systems. This review provides a comprehensive overview of the advancements and applications of nanomaterial-based biosensing systems. Beginning with an exploration of the fundamental principles governing nanomaterials, we delve into their diverse properties, including but not limited to electrical, optical, magnetic, and thermal characteristics. The integration of these nanomaterials as transducers in biosensors has paved the way for unprecedented developments in analytical techniques. Moreover, the principles and types of biosensors and their applications in cardiovascular disease diagnosis are explained in detail. The current biosensors for cardiac biomarker detection are also discussed, with an elaboration of the pros and cons of existing platforms and concluding with future perspectives.

Exploration of molecular interaction between different plant proteins and 2-pentylfuran: based on multiple spectroscopy and molecular docking

BACKGROUND

Soy protein, peanut protein and wheat protein are commonly applied in plant-based products, but specific off-odor makes it difficult for consumers to accept, with 2-pentylfuran being one of the most representative flavors. In this study, 2-pentylfuran was employed as an example to explore the behavior and mechanism of the three proteins in absorbing off-odors.

RESULTS

Gas chromatographic-mass spectrometric analysis indicated that different plant proteins were able to adsorb 2-pentylfuran. Circular dichroism proved 2-pentylfuran could drive the α-helix to β-sheet transition of soy protein, which was not obvious in peanut protein or wheat protein. Ultraviolet spectroscopy tentatively determined that 2-pentylfuran caused changes in the tyrosine and tryptophan microenvironments of different plant proteins, which were further evidenced by synchronous fluorescence at fixed wavelength intervals of 15 nm and 60 nm. Static quenching of protein intrinsic fluorescence indicated that they formed a stable complex with 2-pentylfuran, except for wheat protein (dynamic quenching).

CONCLUSION

The various conformations of the three proteins are the main reason for the difference in flavor retention of protein. Soy protein, peanut protein and wheat protein adsorbing 2-pentylfuran relies on non-covalent forces, especially hydrophobic interactions, maintained between the protein and 2-pentylfuran. © 2023 Society of Chemical Industry.

Probing the Interactions of Lamotrigine and Phenobarbital with Tau Protein: Experimental and Molecular Modeling Studies

Tau, as a small protein in neurons, plays a main role in stabilizing and assembling the internal microtubules. Here, the effects of antiepileptic drugs, including lamotrigine (LTG) and phenobarbital (PHB), on tau protein structure have been investigated by surface plasmon resonance (SPR), fluorescence spectroscopy along molecular modeling. Fluorescence data analysis revealed that both drugs quench the intrinsic emission intensity of tau protein via a static quenching mechanism. Analysis of SPR data at three different temperatures revealed that binding of LTG and PHB to tau protein leads to a decrease and increase in equilibrium constants (K_D) values with increasing temperature, respectively. Therefore, the affinity of LTG decreases and PHB increases with increasing temperature. In addition, molecular docking studies indicated that both LTG and PHB bind to the S1 pocket of tau protein. Our data demonstrated the preventive effect of two important antiepileptic pharmaceuticals on the aggregation of tau protein. Given that any damage to the tau protein possibly leads to neurodegenerative diseases, this study can provide useful and important information and a basis for further research and study to treat tauopathy.

Analysis of drug interactions with serum proteins and related binding agents by affinity capillary electrophoresis: A review

Biomolecules such as serum proteins can interact with drugs in the body and influence their pharmaceutical effects. Specific and precise methods that analyze these interactions are critical for drug development or monitoring and for diagnostic purposes. Affinity capillary electrophoresis (ACE) is one technique that can be used to examine the binding between drugs and serum proteins, or other agents found in serum or blood. This article will review the basic principles of ACE, along with related affinity-based capillary electrophoresis (CE) methods, and examine recent developments that have occurred in this field as related to the characterization of drug-protein interactions. An overview will be given of the various formats that can be used in ACE and CE for such work, including the relative advantages or weaknesses of each approach. Various applications of ACE and affinity-based CE methods for the analysis of drug interactions with serum proteins and other binding agents will also be presented. Applications of ACE and related techniques that will be discussed include drug interaction studies with serum agents, chiral drug separations employing serum proteins, and the use of CE in hybrid methods to characterize drug binding with serum proteins.

Evaluation of the adsorption capacity and mechanism of soy protein isolate for volatile flavor compounds: Role of different oxygen-containing functional groups

Mechanism of soy protein isolate (SPI) adsorbing isomers of volatile flavor compounds (VFCs: 2-octanone, 1-octen-3-ol and octanal) were investigated by exploring the interaction between different oxygen-containing functional groups (OCF groups: carbonyl, alcohol hydroxyl and aldehyde group) and SPI in this study. VFCs made SPI aggregate into larger particle size, and an increase in β-sheet and β-turn was observed. Octanal has strongest binding capacity to SPI, followed by 1-octen-3-ol and 2-octanone. Fluorescence analysis revealed that static quenching occurred between the VFCs and SPI, which suggested that SPI-VFCs complex were formed. Double logarithmic Stern-Volmer indicated the strongest interaction between aldehyde group and SPI, which was proved by surface plasmon resonance. Finally, molecular docking results showed more hydrogen bonds between octanal and SPI. The results showed that aldehyde groups were more likely to interact with SPI than others, probably due to their tendency to form more hydrogen bonds.

Interaction of bovine serum albumin with ellagic acid and urolithins A and B: Insights from surface plasmon resonance, fluorescence, and molecular docking techniques

Human serum albumin (HSA) shows the sequence homology and structural similarity with bovine serum albumin (BSA). Therefore, here, the interaction of natural phenolic antioxidants, ellagic acid (ELA), and its derivatives-urolithins A (ULA) and B (ULB)-with BSA was investigated. The results of surface plasmon resonance (SPR) indicated a high affinity of ELA, ULA, and ULB to BSA, with KD value < 1 × 10-6 M. The KD values of binding of the studied compounds to BSA increased with temperature, revealing a reduction in affinity with an increase in temperature. Fluorescence data showed that the quenching of BSA by tested compounds occurred via a static quenching. However, the affinity of ELA for BSA was higher than that of ULA and ULB, which may be because of the presence of a large number of hydroxyl groups in its structure. The assessment of the antioxidant activity of BSA and BSA-ELA/ULA/ULB complexes using the DPPH assay indicated that the DPPH scavenging activity of BSA increased after complex formation with ELA/ULA/ULB in the following order: BSA-ELA > BSA-ULA > BSA-ULB > BSA, which was due to their structural differences. The results of the docking analysis were in agreement with the experimental results.

Luminescence studies of binding affinity of vildagliptin with bovine serum albumin

Vildagliptin (VDG)is a frontier drug for diabetes mellitus. It is prescribed both in the monotherapy as well as in an amalgamation with other antidiabetic drugs. Drug-serum protein binding is an essential parameter which influences ADME properties of the drug. In current study, binding of VDG with serum protein (bovine serum albumin: BSA) was investigated using multi-spectroscopic techniques. A computational approach was also employed to identify the binding affinity of VDG with BSA at both Sudlow I and II sites. An enzyme activity assay specific for esterase was also investigated to know the post-binding consequences of VDG with BSA. Fluorescence spectra of BSA samples treated with VDG shows static quenching with binding parameters for VDG-BSA complex show single class of equivalent binding stoichiometry(n = 1.331) and binding constant 1.1 x 10⁴M^-1 at 298.15 K. The binding constant indicates important role of non-polar interactions in the binding process. Fluorescence resonance energy transfer (FRET) analysis of VDG absorption spectra and emission spectrum of BSA confirmed no significant resonance in energy transfer. Synchronous fluorescence of BSA after binding with VDG show maximum changes in emission intensity at tryptophan (Trp) residues. Post binding with VDG, BSA conformation changes as suggested by circular dichorism (CD) spectra of BSA and this lead to enhanced protein stability as indicated by a thermal melting curve of BSA.Communicated by Ramaswamy H. Sarma.

Exploring The Interactions of a Natural Gamma-Oryzanol with Human Serum Albumin: Surface Plasmon Resonance, Fluorescence, and Molecular Modeling Studies

γ-oryzanol (ORY) is the vital bioactive compound, which is a mixture of ferulic acid ester and plant sterols. In the present work, the binding of ORY to human serum albumin (HSA) was investigated at the molecular level using fluorescence spectroscopy and surface plasmon resonance (SPR) as well as molecular modeling studies. Based on the fluorescence data analysis, ORY can form a non-fluorescent complex with HSA and induce static quenching of the emission intensity of HSA. Also, the high value of K _SV (34.69 × 10⁴ M^-1) confirmed a high sensitivity of HSA toward ORY. The real-time monitoring of the binding of ORY to HSA was carried out using the SPR technique. The small K _D value (1.23 × 10^-6 M) calculated by SPR analysis indicated a high affinity of ORY toward HSA. The molecular modeling studies confirmed that ORY has only one binding site on HSA and binds HSA in a cavity between subdomain IIA and IIIA.

Exploring the potential of novel phenolic compounds as potential therapeutic candidates against SARS-CoV-2, using quantum chemistry, molecular docking and dynamic studies

In the current study, the interaction of SARS-CoV-2 protein (A and B chains of nsp13) with different recently synthesized phenolic compounds (Sreenivasulu et al., Synthetic Communications, 2020, 112-122) has been studied. The interactions have been investigated by using molecular docking, quantum chemical and molecular dynamics simulations methods. The molecular structures of all the ligands are studied quantum chemically in terms of their optimized structures, 3-D orbital distributions, global chemical descriptors, molecular electrostatic potential plots and HOMO-LUMO orbital energies. All the ligands show reasonably good binding affinities with nsp-13 protein. The ligand L2 shows to have better binding affinities to Chain A and Chain B of nsp13 protein, which are -6.7 and -6.4 kcal/mol. The study of intermolecular interactions indicates that L2 shows different hydrophobic and hydrogen bond interactions with both chains. Furthermore, molecular dynamic simulations of the nsp13-L2 complex are obtained over a time scale of 60 ns, which indicates its stability and flexibility behavior as assessed in terms of its RMSD and RMSF graphs. The ADMET analysis also shows no violation of Lipinski rule (RO5) by studied phenolic compounds. We believe that the current findings will be further confirmed by in vitro and in vivo studies of these recent phenolic compounds for their potential as inhibitors for SARS-Co-V-2 virus.

Understanding the effects of different residual lignin fractions in acid-pretreated bamboo residues on its enzymatic digestibility

BACKGROUND

During the dilute acid pretreatment process, the resulting pseudo-lignin and lignin droplets deposited on the surface of lignocellulose and inhibit the enzymatic digestibility of cellulose in lignocellulose. However, how these lignins interact with cellulase enzymes and then affect enzymatic hydrolysis is still unknown. In this work, different fractions of surface lignin (SL) obtained from dilute acid-pretreated bamboo residues (DAP-BR) were extracted by various organic reagents and the residual lignin in extracted DAP-BR was obtained by the milled wood lignin (MWL) method. All of the lignin fractions obtained from DAP-BR were used to investigate the mechanism for interaction between lignin and cellulase using surface plasmon resonance (SPR) technology to understand how they affect enzymatic hydrolysis RESULTS: The results showed that removing surface lignin significantly decreased the yield for enzymatic hydrolysis DAP-BR from 36.5% to 18.6%. The addition of MWL samples to Avicel inhibited its enzymatic hydrolysis, while different SL samples showed slight increases in enzymatic digestibility. Due to the higher molecular weight and hydrophobicity of MWL samples versus SL samples, a stronger affinity for MWL (KD = 6.8-24.7 nM) was found versus that of SL (KD = 39.4-52.6 nM) by SPR analysis. The affinity constants of all tested lignins exhibited good correlations (r > 0.6) with the effects on enzymatic digestibility of extracted DAP-BR and Avicel.

CONCLUSIONS

This work revealed that the surface lignin on DAP-BR is necessary for maintaining enzyme digestibility levels, and its removal has a negative impact on substrate digestibility.

Probing the interaction between 7-geranyloxycoumarin and bovine serum albumin: Spectroscopic analyzing and molecular docking study

7-Geranyloxycoumarin (auraptene; AUR), as a potent phytochemical, is the naturally abundant prenyloxycoumarin found in many genera of the Rutaceae family. As the interaction with serum albumins may play a crucial role in identifying their pharmacological properties, we investigated AUR binding profile with bovine serum albumin (BSA) by experimental and computational methods. Binding constant, binding site, mode of binding, and the BSA structural change upon AUR addition, were studied. UV-vis spectroscopy results and fluorescence quenching analysis proposed that AUR can form the ground state complex with BSA. Meantime, thermodynamic parameters (negative ΔH and ΔS values) revealed that hydrogen bonds and van der Waals interactions play major role, as intermolecular forces, in the AUR-BSA complex formation. Synchronous fluorescence spectra and circular dichroism (CD) data showed that the secondary structure of BSA did not change significantly in the presence of AUR. Moreover, molecular docking results showed that AUR binds to the subdomain IIIB of BSA.

The inefficacy of donepezil on glycated-AChE inhibition: Binding affinity, complex stability and mechanism

Donepezil (DPZ) is a well-known drug for Alzheimer's disease that inhibits acetylcholinesterase activity (AChE). In the present study, the inhibitory effect of DPZ on non-enzymatic glycated-AChE (GLY-AChE) was studied by different experimental and simulation techniques. The initial investigation revealed that glycation process could reduce AChE activity approximately 60% in the pure enzyme and 38% in the extracted crude AChE from neural cells cultured in the presence of high glucose (HG) concentration. It is suggested that glycation of lysine residues on the structure of AChE could change the conformation of the active site (Trp-86 and His-447) in a way that the orientation of acetylcholine interrupted. The further studies indicated that DPZ is although a strong inhibitor for the native enzyme, it is not able to affect the GLY-AChE activity. The K_D values of AChE-DPZ and GLY-AChE-DPZ complexes were estimated to be 1.88 × 10^-9 and 2.10 × 10^-6, respectively. The stability assessment showed that AChE-DPZ complex is more stable than the glycated complex. Our results indicate that, glycation process could impact on the conformation of the residues involved in the DPZ binding cavity on α-helix domain. Therefore, DPZ is not able to bind its specific cavity to induce its inhibitory effects on GLY-AChE.